Lubricating oil composition



United States Patent 2,996,453 LUBRICATING OIL COMPOSITION L'ouise F. Peale, Philadelphia, and Joseph F. Messina, Havertown, Pa., assignors to the United States of America as represented by the Secretary of the Army N0 Drawing. Filed Mar. 30, 1960, Ser. No. 18,779 1 Claim. (Cl. 252-49.8) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to us of any royalty thereon.

This invention relates to the art of lubrication and more particularly concerns a lubricity additive to both synthetic and mineral lubricating oils to provide improved extreme pressure, anti-wear and anti-friction properties thereto.

- As is well known to those familiar with the art, during the past decade or so, machine design has involved the use of smaller gears of the worm and hypoid type which operate under extremely high pressure loads. Consequently, for effective lubricating, lubricants capable of withstanding pressures appreciably higher than those of which ordinary synthetic or mineral type lubricating oil films will rupture have been required.

The ever-increasing demand for extreme pressure lubricants has led to the development of various extreme pressure agents and to their proposed incorporation in both synthetic and mineral lubricating oils in amounts sufiicient to improve their extreme pressure characteristics. The chemically active type of extreme pressure agents are, as is well known in the art, the most widely used. Presumably, these materials possess the property of reacting chemically with the metal surfaces to be lubricated, under the conditions of operation, to produce thereon films or coatings. These films or coatings are capable either of withstanding by themselves the extreme pressure loads or protecting the relatively moving metal surfaces against seizure and scoring.

In addition to the property of being able to withstand extreme pressure loads, there are other important factors that must be considered in evaluating lubricants for hypoid gear systems and the like. Among the most irnportant are the tendency of the lubricant to wear the surfaces of the relatively moving metal surfaces and to offer unnecessary friction therebetween. Numerous materials have been developed in attempts to meet these requirements satisfactorily. Insofar as is known, however, no single additive compound or lubricity agent to both synthetic and mineral lubricating oils imparting good extreme pressure, anti-wear and anti-friction characteristics to the base oil has been found.

Various phosphorus compounds are currently employed as lubricity additives to base oils of synthetic or mineral type. For example, the presently used triphenyl, tritolyl and olelyl lauryl phosphates improve the extreme pressure characteristics of mineral oils but are deficient in anti-wear improvement.

A commercial compound, tricresyl phosphate, while enhancing anti-wear and anti-friction characteristics to both type oils fails to improve their extreme pressure prop erties.

It is therefore a principal object of this invention to provide a lubricity additive or agent capable of being incorporated in synthetic or mineral oils and yet imparting good extreme pressure, anti-wear and anti-friction properties thereto.

It is another object of this invention to provide such an additive wherein the starting materials are relatively inexpensive and abundantly available.

: Leben apparatus.

These and other objects will be apparent as the invention is more fully hereinafter disclosed.

In accordance with these objects it has been discovered that mrnor additives of a selected long chain phosphate to bis(2-ethylhexyl) sebacate and to various mineral oils s amenable therewith. Further, the blended lubricant is characterized by better than satisfactory extreme pressure, anti-wear and anti-friction properties.

The synthetic lubricating oil chosen for the purposes of this rnvention is bis(2-ethylhexyl) sebacate. This oil is typical of the synthetic diester base oils.

The mineral oils selected presented in the tables following are SAE 40 and SAE 90. It is to be understood that the invention is not to be considered as being limited to the specific viscosities as it will be apparent to those skilled in the art that a wide variety of viscosities of mineral oils may be employed in formulating the lubricant contemplated herein. The lubricity additive, which in accordance with this invention is blended with the synthetic or mineral oil, comprises a long chain phosphate dibutyl lauroxypropyl phosphate. To date, its use has been generally restricted to low temperature plasticizing for vinyl chloride polymers and the like. Its structural and may be prepared in various ways but is, for the most part, conveniently prepared by the following method: 3- hydroxypropyl laurate, having a boiling point of 137 to C. at 0.1 to 0.15 mm. was prepared in 50 to 70% yield by refluxing 80 grams of lauric acid, 305 grams of 1,3-propanediol, 200 ml. of toluene, and 2 grams concentrated sulfuric acid for 4.5 hours with azeotropic remov-al of water. The reaction product was washed several times with water to remove excess glycol and catalyst, and was then fractionally distilled. 46 grams of dibutyl chlorophosphate was slowly added to a stirred solution of 3-hydroxypropyl laurate, 11.9 grams of pyridine and ml. anhydrous ether. Dibutyl lauroxypropyl phosphate having a boiling point of 169 to C. at 0.13 mm. was obtained in 50% yield as a colorless, odorless liquid.

1 through 6 weight percent of the dibutyl lauroxypropyl phosphate was intimately blended with each of bis(2- ethylhexyl) sebaoate and varying SAE mineral oils and then subjected to extreme pressure, anti-wear and antifriction evaluation tests. These tests were conducted on conventional laboratory equipment and will not be described in detail, as their operations are well known to those skilled in the art. For example, anti wea'r data were obtained on the Shell 4-ball Wear tester. Extreme pressure data were determined using the well-known F alex and Shell 4-bal'l extreme pressure tester while anti friction data were obtained on a modified Bowden and The operation of the Shell 4-ball testers, if the reader finds it necessary, may be found amply described in an article 'by G. D. Boerlage, Engineering,

vol. 136 (1933), p. 46 et seq. The Falsex extreme pressure tester is described in Lubrication Engineering, September 1946, V. A. Ryan, while the modified Bowden and Leben apparatus appears in The Friction and Lubrication of Solids, F. P. Bowden and D. Tabor, Oxford Clarendon Press, Oxford, England, 1950, pp. 7374.

For purposes of clarity of illustration, the data ob tained in evaluating the aforementioned properties are tabulated separately below.

TABLE COMIHITGHVZ extreme pressure data Falex Shell 4-Bal1 I Ex- Extreme Wt. t-reme Pressure I Per- Pres- Item Oil Additive cent sure No. Addi- Jaw Seizure Weld tive Load Load Load Fail- (Kg. 1\ (Kg) ure,1bs

1 Bis(2-ethyl- None 1,000 50 100 exyl) sebacate 2 do Dibutyl 2 2,000 90' 180 lauroxyp py phosphate s do do 5 1,750 90 150 4 "do Triisopropyl 5 1, 750 80 140 phosphite. 5..- do Diisopropyl 1 1,750 110 160 phosphite. 6 SAE40Min- Nne 600 50 140 eral oil. 7- do Dibut'yl 2 2,000 70 160 e lauroxyn pyl phosphate. 8 do .do 2,750 '120 180 9 do Commercial 2 600 60 140 tricresyl phosphate. l0 do do 5 600 60 140 ll SAEQDMm- None 600 40 100 eral oil 12 do Dibntyl 2 1, 500 90 180 lauroxy- Q Seizure maybe defined as the load at which a significant increase in wear scar diameter takes place.

b Weld may be defined as the load at which the balls fuse together. 6 Unknown.

Item Nos. 4, 5 and 9, triisopropyland diisopropyl phosphates and tricresyl phosphate are presently used as lubricity agents in diester lubricating oils, such as b1s(2- ethylhexyl) sebacate, and the weight percentages shown are believed to be the optimum percentages used commercially.

TABLE II Comparative anti-wear data Shell 4- Wt. Ball Wear Item No. Oil Additive Percent Scar Di- Additive ametcr,

1 Bis (2-ethyl- None 0.859

hexyl) sebaoate. 2 do Dibutyl lam 2 501 oxypropyl 7 phosphate. 2 dn dn 5 587 4 do tricresyl phos- 2 433 phate. 5 do do 5 401 6 SAE 40 Mineral None 734 il. 7 do Dibutyl laur- 2 675 yp py phosphate. R do do i 5 602 9 do Tricresyl phos- 2 556 phate. 10 do do 5 .504 11 SAE 90 Mineral None .637

oil. 12 do Dibutyl laur- 2 630 yp py 13 do 557 14 SAE 90 Com- .525

mercial hy-' poid gear oil.

Item Nos. 4 and 5, tricresyl phosphate, is used extensively as an efiective anti-wear agent in both synthetic and mineral oils.

TABILE III Comparative coef icient of frzctzon data Wt. Coelficient Item No. Additive Percent of Friction Additive 10 None 46 Dihutyl laur- 2 and 5 04 oxypropyl phosphate. Laurie acid 2 l0 Oleic Acid 2 .08 Stearie Acid..- 2 05 Trieresyl phos- 2 07 phate. 7 do Dialkyl acid 2 06 phosphite. 8 Bis(2-ethyl- None 15 hexyl) sheaeate.

9 "do Dibutyl laur- 2 10 yp py phosphate. 10 do do 5 .14 11; do Dialkyl Acid 2 10 Phosphite. 12 90 Mineral None .17

13 do Dibutyl laur- 2 and 5 11 yn pr phosphate. 14 SAE 90 Gorn- 10 mergial hy-i1 01 ear 0 D g W Item 14, hypoid gear oil, is a commercial product containing phosphorus, sulfur and chlorine additives. Items 3, 4, 5, 6, 7 and 11 are commercial additives.

averages of five difiercnt measurements. variance among the five values was confined to within a 10% range.

All values presented in Tables I, H and 111 above are Maximum Although 2 and 5.weight percentages of dibutyl lauroxypropyl phosphate are presented in the tables, it should be understood that intermediate additions wcre found equally satisfactory, that is, between 2 and 5 weight percentages.

From the data hereinabove set forth, it will become apparent that the lubricity additive of the present invention, when confined within the prescribed range of about 2 to 5 weight percent-ages is positive and specific in improving the extreme pressure, anti-wear and anti-friction characteristics of the base oil. While, in a few instances, the dibutyl lauroxypropyl phosphate did not improve a particular characteristic as markedly as one of the commercial additives, it is believed that no know commercial product to date has been found capable of improving all these requirements in both synthetic and mineral type oils.

We claim: A lubricant composition having improved extreme pressebacate and mineral oil.

selected from the group consisting of bis(2-ethylhexyl) References (Iited in the file of this patent UNITED STATES" PATENTS Downing et al. June 9, 1942 Wiley Aug. 9, 1949 FOREIGN PATENTS Great Britain July 22, 1958 OTHER REFERENCES l Atkins et al.: Development of Additives and Lubricating Oil Compositionsjl. and E. Chem, vol.

April 1947, pp. 491-497. 

